CN103117720A - Self-adaptation control gain method in magnetic card decoding chip - Google Patents
Self-adaptation control gain method in magnetic card decoding chip Download PDFInfo
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- CN103117720A CN103117720A CN2013100159579A CN201310015957A CN103117720A CN 103117720 A CN103117720 A CN 103117720A CN 2013100159579 A CN2013100159579 A CN 2013100159579A CN 201310015957 A CN201310015957 A CN 201310015957A CN 103117720 A CN103117720 A CN 103117720A
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Abstract
The invention discloses a self-adaptation control gain method in a magnetic card decoding chip. The method includes the following steps: (1) a controllable amplifying circuit receives a magnetic card analog signal matched with a pre-stage impedance, when a magnetic card clock points at zero, a default maximum gain shift is used, wave form is amplified and then is output to a post-stage peak detection circuit. (2) The peak detection circuit detects the amplified wave form, if the peak value is higher than a high-voltage limit value, a stage of gain amplifying shift is turned down, if the peak value is lower than a low-voltage limit value, a stage of gain amplifying shift is turned up. (3) A later wave form is amplified through adoption of an adjusted gain shift of the last wave form, then peak value detection and shift adjustment in the step (2) are repeated after amplification. (4) At the same time of adjusting the gain shift, a post-stage miler capacitance value is adjusted to adapt to circuit cooperation work. Through the self-adaptation control gain method, the analog signal read from the magnetic card is realized to be converted into a digital signal accurately.
Description
Technical field
The invention belongs to microelectronics technology, relate to adaptive gain control method in a kind of magnetic card Card Reader chip.
Background technology
Magnetic card technique
Nowadays, magnetic card technique has been applied to the every aspect of people's life.Magnetic card is easy to use, and low cost, purposes are very extensive, can be used for making credit card, bank card, subway card, mass transit card, entrance ticket card, phonecard; Electronic game card, ticket, air ticket and various toll management cards etc.Today, we can use magnetic card in many occasions, as having dinner in the dining room, at market shopping, by bus, made a phone call etc.
Magnetic card is a kind of magnetic recording media card.It is made by high strength, resistant to elevated temperatures plastics or papery coating plastic, can be moistureproof, wear-resisting and certain pliability arranged, and easy to carry, use is comparatively reliable and stable.Usually, the one side of magnetic card is printed with the indicative information of explanation, as the plug-in card direction; Another side has magnetosphere or magnetic stripe, has 2-3 magnetic track to record relevant information data.
Magnetic card recorded information principle is, magnetic card is along with the variation of electric current is magnetized to some extent by magnetic head, if current signal (magnetic field intensity in other words) changes by sinusoidal rule, residual flux on magnetic card changes by sinusoidal rule too so, tracer signal just with the remanent magnetism form record of sinusoidal variations, is stored on magnetic card.Above magnetic card, residual magnetic flux density Br plays conclusive effect in the magnetic card course of work.Magnetic card with certain speed by the work magnetic head of coil is housed, magnetic card external magnetic line of force sectioned coil, produce induced electromotive force in coil, thereby transmitted the signal that is recorded.
Magnetic stripe reader
The equipment that coordinates magnetic card to use is called magnetic card read-write equipment.Usually title has: magnetic bar reader, magnetic card read write line, card reader etc.
In magnetic card reader, most important part is the Card Reader chip.Magnetic head is read the data message that records in magnetic stripe with the form of analog signal, be transferred to the Card Reader chip, and chip internal identification analog signal is converted into digital signal, decodes afterwards, reads magnetic strip information, further encrypts, transmits.Use adaptive gain control technology (AGC) will make Card Reader efficient higher in the Card Reader chip.
In magnetic card card reading circuit in the past, owing to not using automatic gain control, when therefore or magnetic card magnetic serious in the card-reading magnetic head wearing and tearing is desalinated, be difficult to correctly read data on magnetic card.
Summary of the invention
The invention provides the method for adaptive control gain in a kind of magnetic card decoding chip, the wearing and tearing due to magnetic stripe on magnetic card have been solved, magnetic weakens, the wearing and tearing of local magnetic characteristic destruction and magnetic head, the factor such as improper of the mode of swiping the card makes the analog voltage signal of magnetic head output present irregular amplitude non-uniform phenomenon, has avoided carrying out analog digital when transforming, easily occur transforming mistake, affect the rear class decoding circuit.
The technical solution used in the present invention is: a kind of method of adaptive control gain in magnetic card decoding chip, and the method comprises the following steps:
1) controlled amplifying circuit receives the magnetic card analog signal through the prime impedance matching, and when the magnetic card clock was zero, acquiescence was used the maximum gain gear, and waveform is amplified, and exports to the rear class peak detection circuit.
2) peak detection circuit detects the waveform after amplification, if peak value surpasses the high voltage limit value, turns down a stage gain and amplifies gear, amplifies gear if peak value lower than the low-voltage limit value, is heightened a stage gain.
3) gain shift that a upper waveform is adjusted is adopted in the amplification of a rear waveform, carry out step 2 again after amplification) in peak value detect and the gear adjustment.
Adjust the Miller capacitance value of rear class when 4) adjusting gain shift with the adaptive circuit co-ordination.
As preferably, described method adopts the control that gains of gear adjustment mode.Described gear Circuit tuning is divided into many grades, so that the waveform peak after amplifying is controlled between high voltage limit value and low-voltage limit value adaptively.
As preferably, described magnetic card clock uses separately to produce the gear of the impedance matching that is fit to the magnetic card signal and the gear of amplifier multiplication factor, the amplifier gain shift of valid data position, back is to be produced by gear and the shape information of digital processing circuit in conjunction with a upper data waveform, and namely digital processing circuit is according to the voltage gain of certain bit data shape information prediction next bit data.
Beneficial effect of the present invention: by this adaptive gain control circuit, the prime signal will be allowed to larger dynamic range, and larger noise signal also can be identified timely, can't be by as useful signal.Use Card Reader chip of the present invention, with respect to existing Card Reader chip, following advantage is arranged: (1) has super wide reading range, and can understand ISO7811 standard amplitude is the card of 30%-200%, can realize the self adaptation adjustment of magnetic card amplitude; (2) though the wearing and tearing of the existing certain degree of magnetic head, but correct reading out data.(3) antijamming capability is stronger, and prime impedance matching network and controllable amplifier input impedance are complementary, and introduces noise measuring mechanism in the peak value detection, can make the anti-interference energy of Card Reader chip stronger.(4) the present invention can adapt to and adopts the hardware decoding circuit but not soft decoding circuit, thus self adaptation on one side, on one side decoding, realize quick Card Reader.(5) the adaptive gain control circuit is exquisite simple, is easy to circuit and realizes.Therefore in the Card Reader chip, the use of adaptive gain control circuit of the present invention will make the Card Reader chip have higher reading performance.
Description of drawings
Fig. 1 is the magnetic card reader magnetic head figure that swipes the card;
Fig. 2 is magnetic card Card Reader chip adaptive gain control circuit frame diagram;
Fig. 3 is that the present invention program's adaptive gain is adjusted flow chart;
Fig. 4 is that the present invention program's voltage adaptive is adjusted principle schematic;
Fig. 5 is adaptive gain control circuit function diagram in the present invention program.
Embodiment
The present invention will be further described below in conjunction with the drawings and specific embodiments.
The present invention is suitable for the circuit design of magnetic card Card Reader chip, coordinates the use of other circuit, can realize accurately reading data on magnetic card.
As shown in Figure 1, magnetic card reader be on reading file magnetic strip information such as credit card.During according to the ISO7810/7811 standard code, after swiping the card, the card reader magnetic head can read the data of 1,2 or 3 tracks when credit card.The data of 1,2,3 tracks generally include the account numeral, account holder's name, and the credit period of card.Except the data that decoding stores, card reader also can extract the magnetic fingerprint of magnetic stripe.
The data that the magnetic card reader magnetic head is read from magnetic stripe, normally the analog difference signal form, after these analog signal dresses are changed to digital signal, can include account data, user name, deadline, magnetic fingerprint etc.The operations such as the digital signal that solves can be stored in card reader, encrypts, transmission.
As shown in Figure 2, in card reading system, card-reading magnetic head is with Information Read-Out in magnetic stripe, form analog difference signal, through after suitable impedance matching network, be transferred to gain adjustable amplifier, peak detection circuit detects the signal peak after amplifying, differentiate amplitude by gain control unit too high or too low, further the gain shift of ride gain adjustable amplifier, make the waveform of amplifier stable output to the rear class decoding circuit.
In specific embodiment, after magnetic head shown in Figure 1 produces analog signal, the coupling that needs the process impedance matching network to carry out impedance, because the input impedance of rear class gain adjustable amplifier is constantly to change with the adjustment of gain shift, therefore more the adaptive of impedance matching network will be arranged, in addition, the magnetic card output signal is small-signal, be easy to be flooded by noise, therefore suitable impedance matching network signal is followed can be with the power delivery of maximum to rear class.Impedance matching network can be realized by tap resistance form.
Gain adjustable amplifier is controlled by the digital gain control unit, and in the present embodiment, gain is carried out minute gear and controlled, and specifically realizes by the adjustment of adjusting operational amplifier input resistance and feedback resistance resistance ratio.The feedback oscillator multiplication factor is divided into 19 grades from 6 times to 180 times, and the gain gradient of every grade is even, is about 1.2, has realized the dynamic range adjustment of 30dB.The amplitude in ISO7811 sign of can reading is 20% to 200% magnetic card.The signal that magnetic card reads is small-signal, after amplifying through gain adjustable amplifier, sends into follow-up analog-to-digital conversion and decoding circuit.And signal advanced key link---the closed-loop feed-back type gain control circuit, at first carrying out peak value detects, and testing result is sent into gain control unit, after advancing the control unit differentiation, select suitable gear value, in digital form control algorithm amplifier input resistance and feedback resistance resistance ratio.Need simultaneously to adjust gain adjustable amplifier output Miller capacitance value, with the characteristics such as amplifier cut off band width under adaptive different gains gear.
Specific implementation flow process such as Fig. 3, flow chart has shown the process of swiping the card, and from the gain shift that initial leading zero training sequence adjustment is fit to, follow-uply carries out the self adaptation adjustment, makes the output waveform amplitude stabilization.Controlled amplifying circuit receives the magnetic card analog signal through the prime impedance matching, and when the magnetic card clock was zero, acquiescence was used the maximum gain gear, and the former training waveforms of taking turns of analog signal are amplified, and exports to the rear class peak detection circuit.Peak detection circuit detects the waveform after amplification, if peak value V surpasses high voltage limit value Vhigh, turn down a stage gain and amplify gear, if peak value V is lower than low-voltage limit value Vlow, heighten a stage gain and amplify gear, if just between high voltage limit value and low-voltage limit value, keep gain shift constant.As shown in Figure 4, Vcom is reference voltage value, and in the present embodiment, the Vcom representative value is 1.2v, and V1 is the threshold voltage that takes a decision as to whether noise, if the signal after amplifying illustrates that lower than the V1 value this signal is noise, ignores.Vlow is dynamic adjusting range minimum voltage value, Vup is dynamic adjusting range minimum voltage value, and Vlow is between Vup being the dynamic adjusting range of crest voltage, and waveform 1 is the stable waveform after self adaptation, waveform 2 is crossed small form for amplitude, and waveform 3 is the excessive waveform of amplitude.Through several training wave periods, make variable gain amplifier reach the best-fit gear, the gain shift that the amplification of a rear waveform adopts a upper waveform to adjust, and constantly carry out peak value and detect, feed back, adjust, carry out the amplification of the signal of useful data, the waveform amplification that output amplitude is stable.Adjust the Miller capacitance value of rear class when adjusting gain shift with the adaptive circuit co-ordination.Adaptive gain is controlled and will constantly be carried out, until a Card Reader finishes.The voltage parameter adjustment can be according to practical application and difference.
Figure 5 shows that in the present invention program, adaptive gain control circuit function realizes design sketch, the simulation magnetic signal of card-reading magnetic head output amplitude irregularity, the stable amplitude wave-shape that output is amplified after the adaptive gain control circuit.
By this adaptive gain control circuit, the prime signal will be allowed to larger dynamic range, and larger noise signal also can be identified timely, can't be by as useful signal.Therefore in the present embodiment, magnetic card reader will have and have a few: have super wide reading range, can understand ISO7811 standard amplitude is the card of 30%-200%, can realize the self adaptation adjustment of magnetic card amplitude; Even the wearing and tearing of the existing certain degree of magnetic head, but correct reading out data.Antijamming capability is stronger, and prime impedance matching network and controllable amplifier input impedance are complementary, and introduces noise measuring mechanism in the peak value detection, can make the anti-interference energy of Card Reader chip stronger.The present invention can adapt to and adopts the hardware decoding circuit but not soft decoding circuit, thus self adaptation on one side, on one side decoding, realize quick Card Reader.Therefore in the Card Reader chip, the use of adaptive gain control circuit of the present invention will make the Card Reader chip have higher reading performance, and the adaptive gain control circuit is exquisite simple simultaneously, is easy to circuit and realizes.
Should be pointed out that for those skilled in the art, under the prerequisite that does not break away from the principle of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.In the present embodiment not clear and definite each part all available prior art realized.
Claims (3)
1. the method for adaptive control gain in a magnetic card decoding chip, it is characterized in that: the method comprises the following steps:
1) controlled amplifying circuit receives the magnetic card analog signal through the prime impedance matching, and when the magnetic card clock was zero, acquiescence was used the maximum gain gear, and waveform is amplified, and exports to the rear class peak detection circuit;
2) peak detection circuit detects the waveform after amplification, if peak value surpasses the high voltage limit value, turns down a stage gain and amplifies gear, amplifies gear if peak value lower than the low-voltage limit value, is heightened a stage gain;
3) gain shift that a upper waveform is adjusted is adopted in the amplification of a rear waveform, carry out step 2 again after amplification) in peak value detect and the gear adjustment;
Adjust the Miller capacitance value of rear class when 4) adjusting gain shift with the adaptive circuit co-ordination.
2. the method that in a kind of magnetic card decoding chip according to claim 1, adaptive control gains, it is characterized in that: described method adopts the control that gains of gear adjustment mode, described gear Circuit tuning is divided into many grades, so that the waveform peak after amplifying is controlled between high voltage limit value and low-voltage limit value adaptively.
3. the method that in a kind of magnetic card decoding chip according to claim 1, adaptive control gains, it is characterized in that: described magnetic card clock uses separately to produce the gear of the impedance matching that is fit to the magnetic card signal and the gear of amplifier multiplication factor, the amplifier gain shift of valid data position, back is to be produced by gear and the shape information of digital processing circuit in conjunction with a upper data waveform, and namely digital processing circuit is according to the voltage gain of certain bit data shape information prediction next bit data.
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| CN2013100159579A CN103117720A (en) | 2013-01-16 | 2013-01-16 | Self-adaptation control gain method in magnetic card decoding chip |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106446739A (en) * | 2016-09-22 | 2017-02-22 | 飞天诚信科技股份有限公司 | Method and apparatus for self-adaptive gain adjustment |
| CN107038397A (en) * | 2017-04-10 | 2017-08-11 | 上海汇尔通信息技术有限公司 | A kind of coding/decoding method and system |
Citations (2)
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| US20110050285A1 (en) * | 2009-08-27 | 2011-03-03 | Qualcomm Incorporated | High linear fast peak detector |
| CN202383709U (en) * | 2011-12-22 | 2012-08-15 | 福建联迪商用设备有限公司 | Novel magnetic card reading circuit structure |
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2013
- 2013-01-16 CN CN2013100159579A patent/CN103117720A/en active Pending
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20110050285A1 (en) * | 2009-08-27 | 2011-03-03 | Qualcomm Incorporated | High linear fast peak detector |
| CN202383709U (en) * | 2011-12-22 | 2012-08-15 | 福建联迪商用设备有限公司 | Novel magnetic card reading circuit structure |
Non-Patent Citations (1)
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| 牛宜超: "磁条卡解码芯片中编码电路的设计", 《中国优秀硕士学位论文全文数据库》 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106446739A (en) * | 2016-09-22 | 2017-02-22 | 飞天诚信科技股份有限公司 | Method and apparatus for self-adaptive gain adjustment |
| CN106446739B (en) * | 2016-09-22 | 2019-03-05 | 飞天诚信科技股份有限公司 | A kind of method and device of adaptive gain regulating |
| CN107038397A (en) * | 2017-04-10 | 2017-08-11 | 上海汇尔通信息技术有限公司 | A kind of coding/decoding method and system |
| CN107038397B (en) * | 2017-04-10 | 2019-12-31 | 上海汇尔通信息技术有限公司 | Decoding method and system |
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Application publication date: 20130522 |